As people's living standards improve, the number of waste printed circuit board (PCB) from waste home appliances is increasing with the upgrade of various home appliances. If discarded directly, such PCB would not only take up a lot of land resources, but also result in a waste of valuable metal resources. In addition, polyvinyl chloride, halide flame retardants and other hazardous substances thereof will cause huge pollution to the surrounding environment. Therefore, how to effectively deal with waste printed circuit board, to realize recycling and reuse of printed circuit board has become a serious problem to be solved.
Recycling techniques used commonly comprise pyrometallurgy, wet cyanidation metallurgy or combination thereof. However, the methods of pyrometallurgy and wet cyanidation metallurgy pollute the environment seriously, especially the traditional wet process cyanidation metallurgy, which may cause great environmental pollution owing to the highly toxic substances cyanide.
Moreover, it is generally limited to the recycling of copper and noble metals (such as gold, silver, platinum and/or palladium) from waste printed circuit board in the prior art, for example, method for recycling copper from waste circuit board disclosed in CN101270411A, and method for extracting gold from waste circuit board disclosed in CN101230421A, however, such methods ignored the recycling of tin, lead, antimony and aluminum from solder.
CN101787547A discloses a method for extracting primary products of copper, nickel, silver, gold, platinum and palladium, and other byproducts of lead, tin, antimony and aluminum from waste printed circuit board, which maximizes the reuse of valuable metal resources. However, the lead-containing byproduct Na2PbO3 and tin-containing byproduct Na2SnO3 are mixed and crystallized in the same step in this method, thus they cannot be completely separated and recycled, and need to return to smelter where lead or tin can be smelted for extraction. Furthermore, the means of recycling metallic silver in such method involves dissolving silver-containing residues in nitric acid solution, and obtaining electrowinning silver after electrowinning Nevertheless, metallic palladium will be also dissolved while silver is dissolved in nitric acid solution, which will lead to a low recycling rate of palladium in the subsequent recycling process.